Polyaryl Ether Ketone (PAEK) forms a family of semi-crystalline thermoplastics with high-temperature stability and high mechanical strength: PAEKs have continuous operating temperatures of 250-280° C., but under short-term loads can function up to about 350-380° C. When subjected to flame, PAEKs have the least toxic and corrosive fumes. PAEKs also have low heat and smoke output under flame, so PAEKs qualify for use in interior aviation applications. PAEKs also demonstrates very good overall chemical resistance. Their tensile strength is of over 85 MPa (12,300 psi) and a Young's modulus of over 4,100 MPa (590,000 psi), making them very strong contenders for metal replacements.
PAEK plastics are characterized by phenylene rings that are linked via oxygen bridges (ether) and carbonyl groups (ketone). The ratio of ether to ketones and their sequence mainly affect the glass transition temperature and melting point of the polymer. They also affect heat resistance and processing temperature. The higher the ratio of ketones to ether, more rigid the polymer chain, which results in a higher glass transition temperature and melting point.
Polyaryl Ether Ketone polymers comprise a number of closely related polymers which include Polyether Ketone (PEK), Polyether Ether Ketone (PEEK), Polyether Ketone Ketone (PEKK), Polyether Keton Ether Ketone Ketone (PEKEKK) and Polyether Ether Ketone Ketone (PEEKK). These polymers are moldable, and thus easily formed into usable parts.
Polybenzimidazole (PBI) is a polymer with extremely high temperature stability. It does not readily ignite and has high chemical resistance. Due to its exceptional thermal and chemical stability, it finds usage where these properties are important. Recently, PBI has received much attention for its use as a high temperature fuel cell membrane. There are two important types of Polybenzimidazole structures: One, also known as ABPBI, is a polymer of 3,4 Diamino Benzoic acid. While commercially available PBI is a polymer of 2,2′ 5,5′ Diamino Biphenyl with Isophthalic Anhydride or its derivatives. ABPBI, though known in literature has found no commercial usage because of its extremely high Glass Transition Temperature range of 450 to 485° C.
Polybenzimidazole and Polyaryl Ether Ketone blends are known for their excellent mechanical, thermal and chemical resistance properties. U.S. Pat. No. 4,912,176 discloses blends of Poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole and Polyarylene Ketones.
U.S. Pat. No. 5,391,605 discloses a polymeric composition comprising from about 65 to about 85 weight percent of a polymeric blend and from about 15 to about 35 weight percent of internal lubricants. The blend consists of from about 35 to about 100 weight percent of an aromatic Polybenzimidazole and from about 0 to about 65 weight percent of Poly(aryl Ether Ketone). The lubricants consist of boron nitride powder and graphite in a weight ratio of about 1:10 to about 10:1.
It is found that the known Polybenzimidazole (PBI) and Polyaryl Ether Ketone blends do not provide very good mechanical and wear resistance properties. Accordingly, it is desirable to develop a composition comprising a blend of Polybenzimidazole and Polyaryl Ether Ketone, which provides higher mechanical and wear resistance properties to the articles made therefrom.